Hantavirus pulmonary syndrome (HPS) is a severe (case fatality = 35%) rodent-borne viral disease of the Americas. Sin Nombre hantavirus (SNV) hosted by the widespread deer mouse (Peromyscus maniculatus) is responsible for the majority of hantavirus pulmonary syndrome (HPS) cases in the United States. The design and implementation of effective disease prevention interventions for HPS and the targeting of these interventions depends upon a detailed knowledge of the factors controlling SNV propagation in host populations. Field studies have identified the primary routes of transmission between mice and humans and among deer mice. However, because of difficulties in achieving natural virus transmission in the laboratory environment, laboratory studies have contributed little to clarifying the dynamics of SNV infection and transmission in deer mouse populations. The main objective of this project is to study the SNV infection cycle and transmission dynamics within enclosed, outdoor deer mouse populations. These controlled field experiments will elucidate the temporal pattern of virus transmission in mice, patterns of viral shedding, and social, demographic, and ecological factors that contribute to the transmission and maintenance of SNV in deer mouse populations. This information is critical to understanding changes in human risk and developing models to predict times and places of increased human disease risk. [unreadable] [unreadable] [unreadable]